The disclosure relates generally to mobile communications systems and related networks, such as Universal Mobile Telecommunications Systems (UMTSs), its offspring Long Term Evolution (LTE) and 5th Generation New Radio (5G-NR) described and being developed by the Third Generation Partnership Project (3GPP), and more particularly to a 5G non-standalone (NSA) radio access system relying on a 4G master connection to enable dual radio data connectivity.
Operators of mobile systems, such as UMTS and its offspring, including LTE and LTE-Advanced, are increasingly relying on wireless small cell radio access nodes (RANs) in order to deploy, for example, indoor voice and data services to enterprises and other customers. Such small cell RANs typically utilize multiple-access technologies capable of supporting communications with multiple users using radio frequency (RF) signals and sharing available system resources such as bandwidth and transmit power. Evolved Universal Terrestrial Radio Access (E-UTRA) is the radio interface of 3GPP's LTE upgrade path for UMTS mobile networks. In these systems, there are different frequencies where LTE (or E-UTRA) can be used, and in such systems, user mobile communications devices connect to a serving system, which is represented by a cell. In LTE, each cell is produced by a node called eNodeB (eNB).
5G radio access system specifications are being developed by 3GPP. 3GPP 5G specifications will be introduced in two phases. Phase 1 is a 5G NSA solution, and phase 2 is a standalone 5G solution (5G SA). In the phase 1 5G NSA solution, a 5G radio link is used in parallel with a 4G radio link in a dual connectivity setup. The 4G radio link is the master radio link, and the 5G radio link is the secondary radio link. The 5G secondary radio link provides an additional high speed data plane between the network and a user mobile communications device (also referred to as “user equipment (UE)”), while the 4G master radio link carries control signaling, including signaling required to establish and maintain the 5G secondary radio link. This 5G NSA solution was selected as the phase 1 solution for 5G deployment as the required amount of specification and development work is much smaller than what is required to enable a 5G SA solution where the 5G system can operate irrespectively of any 4G system.
To enable the phase 1 5G NSA solution, the UE needs to be connected to a 4G radio access system that provides the master radio link for the 4G/5G dual connectivity. The 4G radio access node (RAN) (4G RAN) (e.g., a 4G base station) of the 4G system needs to be able to exchange 5G NSA specific signaling over a direct interface with a 5G RAN (e.g., a 5G base station), such that a 5G connection between UE and the 5G RAN is managed by the 4G RAN. This 5G NSA system architecture can be achieved by either deploying a new 5G NSA compatible 4G RAN, or by using an existing 4G RAN that is updated with new features required to support the 5G NSA architecture. Both of these solutions have drawbacks. For example, deploying a new 4G RAN with new features required to support the 5G NSA architecture implies additional capital and operational expenditure, and typically requires that dedicated 4G spectrum be assigned to the new 4G RAN. Updating an existing 4G RAN to support new features required to support the 5G NSA architecture may involve significant investment to existing 4G RANs. Further, an existing 4G RAN may not support an open interface to a 5G RAN needed to exchange 5G NSA specific signaling between the 4G RAN and a 5G RAN, thus “locking in” a mobile network operator (MNO) to procure their 5G RAN from the same vendor as their 4G RAN.
No admission is made that any reference cited herein constitutes prior art. Applicant expressly reserves the right to challenge the accuracy and pertinency of any cited documents.